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Trace: • Modern Processors: Cache, Pipeline, Superscalar, Branch Prediction, Hyperthreading • DMA • Software Systems and Middleware • Fundamentals of Data Encoding, Big Endian, Little Endian

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en:multiasm:papc:chapter_6_3 [2025/12/22 11:34] – [x86 registers] ktokarzen:multiasm:papc:chapter_6_3 [2026/04/01 14:03] (current) – [ZMM registers] ktokarz
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 ====== Register Set ====== ====== Register Set ======
 +As x86 processors evolved, the set of available registers and their size expanded. Newer processors added more general-purpose registers, and new registers related to the FPU and vector extensions were added. In this chapter, we discuss the registers available to the programmer, from the 8086 up to modern 64-bit processors.
 ===== x86 registers ===== ===== x86 registers =====
 The 8086 processor has seven general-purpose registers for data storage, data manipulation and indirect addressing. Four registers: AX, BX, CX and DX can be accessed in two 8-bit halves. The lower half has the "L" letter, and the upper half has the "H" letter in the register name instead of "X". General-purpose registers are presented in Fig {{ref>gpregistresx86}}. The 8086 processor has seven general-purpose registers for data storage, data manipulation and indirect addressing. Four registers: AX, BX, CX and DX can be accessed in two 8-bit halves. The lower half has the "L" letter, and the upper half has the "H" letter in the register name instead of "X". General-purpose registers are presented in Fig {{ref>gpregistresx86}}.
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 </figure> </figure>
 ===== XMM registers ===== ===== XMM registers =====
-SSE instructions are executed with the use of 128-bit packed data. To perform calculations, new 128-bit registers were introduced. The SSE unit has 8 registers named XMM0 - XMM7, as presented in figure {{ref>xmmregs}}. Because these registers are separate from all previous ones, there are no conflicts between SSE and other instructions. +SSE instructions are executed with the use of 128-bit packed data. To perform calculations, new 128-bit registers were introduced. The SSE unit has 8 registers named XMM0 - XMM7. Because these registers are separate from all previous ones, there are no conflicts between SSE and other instructions.
- +
-<figure xmmregs> +
-{{ :en:multiasm:cs:xmm_registers.png?500 |Illustration of the 128-bit XMM registers}} +
-<caption>128-bit XMM registers</caption> +
-</figure>+
  
 To control the behaviour and to provide information about the status of the SSE unit, the MXCSR register is implemented (figure {{ref>mxcsrreg}}). It is a 32-bit register with bits with their functions similar to the FPU unit's Control Word and Status Word registers concatenated together. To control the behaviour and to provide information about the status of the SSE unit, the MXCSR register is implemented (figure {{ref>mxcsrreg}}). It is a 32-bit register with bits with their functions similar to the FPU unit's Control Word and Status Word registers concatenated together.
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 </figure> </figure>
 ===== YMM registers ===== ===== YMM registers =====
-The YMM registers are the 256-bit extension to the XMM registers. They are introduced to implement the AVX set of instructions. Additionally, in 64-bit processors, the number of available YMM registers was increased to 16 (figure {{ref>ymmregs}}). +The YMM registers are the 256-bit extension to the XMM registers. They are introduced to implement the AVX set of instructions. Additionally, in 64-bit processors, the number of available YMM registers was increased to 16.
- +
-<figure ymmregs> +
-{{ :en:multiasm:cs:ymm_registers.png?600 |Illustration of the 256-bit YMM registers}} +
-<caption>256-bit YMM registers</caption> +
-</figure>+
 ===== ZMM registers ===== ===== ZMM registers =====
-ZMM registers are the further extension of XMM registers to 512 bits. In 64-bit machines, 32 of such registers are available (figure {{ref>zmmregs}}). +ZMM registers are the further extension of XMM registers to 512 bits. In 64-bit machines, 32 of such registers are available.
- +
-<figure zmmregs> +
-{{ :en:multiasm:cs:zmm_registers.png?600 |Illustration of the 512-bit ZMM registers}} +
-<caption>512-bit ZMM registers</caption> +
-</figure>+
 XMM are the physical lower halves of YMM, which are the lower halves of ZMM. Anything written to the XMM register appears in part of the YMM and ZMM registers as presented in figure {{ref>xyzmmregs}} XMM are the physical lower halves of YMM, which are the lower halves of ZMM. Anything written to the XMM register appears in part of the YMM and ZMM registers as presented in figure {{ref>xyzmmregs}}
  
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 <caption>The relation between XMM, YMM and ZMM registers</caption> <caption>The relation between XMM, YMM and ZMM registers</caption>
 </figure> </figure>
-Together with AVX extension and ZMM registers, eight 16-bit opmask registers were introduced to x64 processors (figure {{ref>opmaskregs}}). They can be used, e.g. to provide conditional execution or mask several elements of vectors in AVX instructions. +Together with AVX extension and ZMM registers, eight 16-bit opmask registers were introduced to x64 processors. They can be used, e.g. to provide conditional execution or mask several elements of vectors in AVX instructions.
- +
-<figure opmaskregs> +
-{{ :en:multiasm:cs:opmask_registers.png?400 |Illustration of the opmask registers}} +
-<caption>Opmask registers</caption> +
-</figure>+
  
  
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